self.KeyWS_Pressed = falseThe errors result from streamWriteBool trying to write "nil" values, which it cannot do. It has to be boolean, true or false (though "nil" can be equal to false in Lua, a "nil" variable is not a boolean value for a write).

I've never seen this mod before today, the edits I listed are untested (I still haven't used this mod), your mileage may vary.